Patent GB-203653-A (GB)
Abstract: 203,653. Automatic Telephone Manufacturing Co., Ltd., (Assignees of Sipe, C. R.). Sept. 11, 1922, [Convention date]. Autoinatic exchange systems.-A rotary connector having access to a large group of private branch exchange lines occupying several complete levels and part of other levels, after being raised according to the penultimate digit, is rotated according to the last digit to the first line of the group if there is an idle line in that level, but otherwise is raised automatically until a level is reached in which there is an idle line, the last digit being ineffective in this case. In the example given, one P.B.X. group occupies the 1st and 2nd levels and part of the 3rd level, while a second P.B.X. group occupies the remainder of the 3rd level and the 4th level. Chain relays 18 are connected to the test terminals such as 81 of all the lines except those in the top level of the group, so that if all the lines in a level are busy, earth is connected to one of two vertical test terminals such as 94, 95 engaged bv vertical test wipers 90, 91 to raise the wipers to the next level. The test terminals such as 24 of the lines in the top level of the group are connected to battery through a resistance, and hunting takes place over this level even if all the lines are busy. Connection to an idle line of the first P.B.X. group. At the end of the first set of impulses, the vertical magnet 15 and the series relay 6 release, and connect a vertical stepping relay 7 and a vertical wiper relay 8 to the vertical test wiper 90, so that these relays energize if all the lines in the level are busy. The relay 8 opens the rotary magnet circuit and transfers the vertical test circuit to the wiper 91. The relay 7 connects up the vertical magnet 15, which interacts with the relay 7 to raise the wipers so long as the wiper 91 engages earthed terminals, the slow relay 6 holding the rotary magnet circuit open meanwhile. When a level containing an idle line is reached, the relay 7 no longer energizes, and upon release of the relay 6, the rotary magnet 16 and a slow relay 13 are energized in parallel, and the latter connects the test relay 12 to the test wiper 77. A rotary stepping relay 9 which was energized by the relays 6, 8 now interacts with the rotary magnet 16 to step the wipers until an idle line is reached, the relay 9 being energized over the strapped terminals like 80, 81 in the case of a busy line by the operation of the test relay 12. When an idle line is seized, the relay 13 releases and connects up the switching relay 14 in series with the chain relay 18, earthing the test terminal 81, locking the chain relay and applying ringing current to the selected line, whereupon the connection is completed in the usual manner. If all the lines in the group are busy, the wipers are raised to the 3rd level and hunt over that level. The terminals 23, 24 of the last line of the group are not strapped together, so that relay 9 does not energize upon operation of the test relay 12, and the release of the relay 13 sends back a busy signal. The terminals of the last lines of a level are also not strapped together, so that if there is only one idle line in that level and two connectors start rotating nearly simultaneously, the second gives a busy signal on reaching the last line of the level. Connection to an idle line of the. second P.B.X. group. The wipers are raised to the 3rd level by the first set of impulses, and if there is an idle line in that level, the connector responds to the last digit to move the wipers to the. first line of the group, the rotary magnet 16 being energized in series with the slow relay 11 in the usual manner. If all the lines in the 3rd level are busy, the wipers are raised by earth potential on the test terminal 96, and the last set of impulses is now ineffective since the normal rotary magnet circuit is broken by the relay 8. Small groups of lines. These are connected up and are selected from in the same way as the top level of a large group.